On unix, the rscd install is part of the appserver installer, so normally during the appserver (or nsh) install you would select to install the appserver and the rscd. when you use the appserver installer to upgrade then the agent that is part of this install would be upgraded.

If you used the rscd or other installer to run another install (w/ the –local option) on the same box, then you would need to separately upgrade this agent. there’s a section in the product docs about upgrading the ‘local’ install agent. https://docs.bmc.com/docs/display/bsa83/UpgradingcomponentsusingthelocaloptiononUNIXor+Linux